“I, and I alone am ALLAH. There cannot be, is no other and will never be One worthy of worship but I, therefore worship Me alone. And observe prayer so that you may keep Me in mind.”
[20:14 – Amatul Rahman Omar]

The Prophet (pbuh) has said:

[Hadith – Muslim, Book#001, Hadith #0047] “It is narrated on the authority of Mu'adh b. Jabal that he observed: I was riding behind the Messenger of Allah (may peace be upon him) on an ass known as 'Ufair. He (Mu'adh) observed: He (the Holy Prophet) said: Mu'adh, do you know what right has Allah over His bondsmen and what right have His bondsmen over Him? Mu'adh added: I replied: Allah and his Messenger know best. Upon this he (the Holy Prophet remarked: The right of Allah over His bondsmen is that they should worship Allah and should not associate anything with Him, and the right of His bondsmen over Allah, Glorious and Sublime, is that He does not punish him who associates not anything with Him. He (Mu'adh) added: I said to the Messenger of Allah: Should I then give the tidings to the people? He (the Holy Prophet) said: Do not tell them this good news, for they would trust in it alone.”